Colm J McMahon

Publications (11)29.22 Total impact

• Article: High-resolution proton density weighted three-dimensional fast spin echo (3D-FSE) of the knee with IDEAL at 1.5 Tesla: comparison with 3D-FSE and 2D-FSE--initial experience.

  Colm J McMahon, Ananth J Madhuranthakam, Jim S Wu, Corrie M Yablon, Jesse L Wei, Neil M Rofsky, Mary G Hochman
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  ABSTRACT: To assess the feasibility of combining three-dimensional fast spin echo (3D-FSE) and Iterative-decomposition-of water-and-fat-with-echo asymmetry-and-least-squares-estimation (IDEAL) at 1.5 Tesla (T), generating a high-resolution 3D isotropic proton density-weighted image set with and without "fat-suppression" (FS) in a single acquisition, and to compare with 2D-FSE and 3D-FSE (without IDEAL). Ten asymptomatic volunteers prospectively underwent sagittal 3D-FSE-IDEAL, 3D-FSE, and 2D-FSE sequences at 1.5T (slice thickness [ST]: 0.8 mm, 0.8 mm, and 3.5 mm, respectively). 3D-FSE and 2D-FSE were repeated with frequency-selective FS. Fluid, cartilage, and muscle signal-to-noise ratio (SNR) and fluid-cartilage contrast-to-noise ratio (CNR) were compared among sequences. Three blinded reviewers independently scored quality of menisci/cartilage depiction for all sequences. "Fat-suppression" was qualitatively scored and compared among sequences. 3D-FSE-IDEAL fluid-cartilage CNR was higher than in 2D-FSE (P < 0.05), not different from 3D-FSE (P = 0.31). There was no significant difference in fluid SNR among sequences. 2D-FSE cartilage SNR was higher than in 3D FSE-IDEAL (P < 0.05), not different to 3D-FSE (P = 0.059). 2D-FSE muscle SNR was higher than in 3D-FSE-IDEAL (P < 0.05) and 3D-FSE (P < 0.05). Good or excellent depiction of menisci/cartilage was achieved using 3D-FSE-IDEAL in the acquired sagittal and reformatted planes. Excellent, homogeneous "fat-suppression" was achieved using 3D-FSE-IDEAL, superior to FS-3D-FSE and FS-2D-FSE (P < 0.05). 3D FSE-IDEAL is a feasible approach to acquire multiplanar images of diagnostic quality, both with and without homogeneous "fat-suppression" from a single acquisition.
  Journal of Magnetic Resonance Imaging 02/2012; 35(2):361-9. · 2.70 Impact Factor
• Article: Automated computer-derived prostate volumes from MR imaging data: comparison with radiologist-derived MR imaging and pathologic specimen volumes.

  Julie C Bulman, Robert Toth, Amish D Patel, B Nicolas Bloch, Colm J McMahon, Long Ngo, Anant Madabhushi, Neil M Rofsky
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  ABSTRACT: To compare prostate gland volume (PV) estimation of automated computer-generated multifeature active shape models (MFAs) performed with 3-T magnetic resonance (MR) imaging with that of other methods of PV assessment, with pathologic specimens as the reference standard. All subjects provided written informed consent for this HIPAA-compliant and institutional review board-approved study. Freshly weighed prostatectomy specimens from 91 patients (mean age, 59 years; range, 42-84 years) served as the reference standard. PVs were manually calculated by two independent readers from MR images by using the standard ellipsoid formula. Planimetry PV was calculated from gland areas generated by two independent investigators by using manually drawn regions of interest. Computer-automated assessment of PV with an MFA was determined by the aggregate computer-calculated prostate area over the range of axial T2-weighted prostate MR images. Linear regression, linear mixed-effects models, concordance correlation coefficients, and Bland-Altman limits of agreement were used to compare volume estimation methods. MFA-derived PVs had the best correlation with pathologic specimen PVs (slope, 0.888). Planimetry derived volumes produced slopes of 0.864 and 0.804 for two independent readers when compared with specimen PVs. Ellipsoid formula-derived PVs had slopes closest to one when compared with planimetry PVs. Manual MR imaging and MFA PV estimates had high concordance correlation coefficients with pathologic specimens. MFAs with axial T2-weighted MR imaging provided an automated and efficient tool with which to assess PV. Both MFAs and MR imaging planimetry require adjustments for optimized PV accuracy when compared with prostatectomy specimens.
  Radiology 01/2012; 262(1):144-51. · 5.73 Impact Factor
• Article: Prevalence of renal artery stenosis in flash pulmonary oedema: determination using gadolinium-enhanced MRA.

  Colm J McMahon, Martina Hennessy, Gerard Boyle, John Feely, James F M Meaney
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  ABSTRACT: The primary purpose was to determine the prevalence of renal artery stenosis (RAS) in patients presenting with acute ("flash") pulmonary oedema (FPE), without identifiable cause using contrast-enhanced magnetic resonance angiography (CE-MRA) of renal arteries. A secondary goal was to correlate clinical parameters at presentation with the presence or absence of RAS. Patients presenting with acute pulmonary oedema without identifiable cause prospectively underwent CE-MRA. >50% renal artery stenosis was considered significant. Clinical parameters (blood pressure, serum creatinine, history of hypertension/hyperlipidaemia) were compared in patients with and without RAS using an unpaired t-test. Results expressed; mean (+/-SD). 20 patients (4 male, 16 female, age 78.5+/-11 years) underwent CE-MRA. 9 patients (45%) had significant RAS (6 (30%) bilateral, 3 (15%) unilateral). Systolic BP was higher in patients with RAS (192+/-38 mm Hg) than those without (134+/-30 mm Hg) (p<.005). Diastolic BP was higher in patients with RAS (102+/-23 mm Hg) than those without (76+/-17 mm Hg) (p<.01). All patients with RAS and 6/11(55%) patients without RAS had a history of hypertension. No significant difference in creatinine or hyperlipidaemia history was observed. The prevalence of RAS in patients presenting with FPE is 45%. The diagnosis should be considered in patients presenting with unexplained acute pulmonary oedema, particularly if hypertensive at presentation.
  European Journal of Internal Medicine 10/2010; 21(5):424-8. · 2.00 Impact Factor
• Article: Muscle edema.

  Colm J McMahon, Jim S Wu, Ronald L Eisenberg
  American Journal of Roentgenology 04/2010; 194(4):W284-92. · 2.78 Impact Factor
• Article: An unusual variant of anomalous pancreaticobiliary junction in a patient with pancreas divisum diagnosed with secretin-magnetic resonance cholangiopancreatography.

  Colm J McMahon, Charles M Vollmer, Jeffrey Goldsmith, Alphonso Brown, Douglas Pleskow, Ivan Pedrosa
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  ABSTRACT: Anomalous pancreaticobiliary junction is an unusual variant of pancreaticobiliary anatomy of clinical importance because it is associated with increased risk of pancreatitis and, also, for the development of cholangiocarcinoma. We report an unusual variant of anomalous pancreaticobiliary junction, occurring in a patient with pancreas divisum, with an anomalous communication between the dorsal pancreatic and the common bile duct. The patient presented with a distal biliary stricture. This variant anatomy was occult on magnetic resonance cholangiopancreatography but was diagnosed on magnetic resonance cholangiopancreatography that was performed with intravenous secretin administration and further delineated by endoscopic retrograde cholangiopancreatography. The features that allowed the diagnosis to be made and the implications of this diagnosis are described in this report.
  Pancreas 01/2010; 39(1):101-4. · 2.39 Impact Factor
• Article: Lymphatic metastases from pelvic tumors: anatomic classification, characterization, and staging.

  Colm J McMahon, Neil M Rofsky, Ivan Pedrosa
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  ABSTRACT: The spread of pelvic tumors to lymph nodes is an important means of tumor dissemination. Nodal metastases have important management and prognostic impact. Pelvic tumors usually metastasize first to regional lymph nodes, which are specific groups of nodes for each tumor, and are classified according to the TNM system as N-stage disease. If a pelvic tumor spreads to a lymph node outside of the defined regional nodes, this is considered M-stage disease, which usually results in upstaging of the disease to overall stage IV cancer and may potentially affect the patient's treatment options. Knowledge of the regional nodal spread of each tumor is essential in formulating effective search strategies for cross-sectional imaging studies performed for staging. Also important is correct description of the nomenclature of nodal metastases to facilitate proper staging. In this review, the patterns of regional nodal spread and N-stage classification are presented for carcinomas of the anus, bladder, cervix, endometrium, ovary, penis, prostate, rectum, testis, vagina, and vulva. Pelvic lymph node anatomy and nomenclature are reviewed with schematic illustrations and clinical examples from patients with pelvic tumors.
  Radiology 01/2010; 254(1):31-46. · 5.73 Impact Factor
• Article: Dynamic contrast-enhanced MR imaging in the evaluation of patients with prostate cancer.

  Colm J McMahon, B Nicolas Bloch, Robert E Lenkinski, Neil M Rofsky
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  ABSTRACT: Prostate cancer is a common tumor among men, with increasing diagnosis at an earlier stage and a lower volume of disease because of screening with prostate-specific antigen (PSA). The need for imaging of the prostate stems from a desire to optimize treatment strategy on a patient and tumor-specific level. The major goals of prostate imaging are (1) staging of known cancer, (2) determination of tumor aggressiveness, (3) diagnosis of cancer in patients who have elevated PSA but a negative biopsy, (4) treatment planning, and (5) the evaluation of therapy response. This article concentrates on the role of dynamic contrast-enhanced MR imaging in the evaluation of patients who have prostate cancer and how it might be used to help achieve the above goals. Various dynamic contrast enhancement approaches (quantitative/semiquantitative/qualitative, high temporal versus high spatial resolution) are summarized with reference to the relevant strengths and compromises of each approach.
  Magnetic resonance imaging clinics of North America 06/2009; 17(2):363-83.
• Article: Magnetic resonance imaging in locoregional staging of rectal adenocarcinoma.

  Colm J McMahon, Martin P Smith
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  ABSTRACT: A comprehensive overview of the current status of magnetic resonance imaging (MRI) in the locoregional assessment and management of rectal adenocarcinoma is presented. Staging systems for rectal cancer and treatment strategies in its management are discussed to give the reader the context that shapes MRI acquisition techniques and interpretation. Findings on MRI are detailed and their accuracy reviewed based on currently available evidence. Optimization of MRI acquisition and relevant pelvic anatomy are reviewed. A detailed description of our approach in interpreting MRI for locoregional staging of rectal cancer is given and future directions are also introduced.
  Seminars in Ultrasound CT and MRI 01/2009; 29(6):433-53. · 1.24 Impact Factor
• Source

  Available from: Edwin van Beek

  Article: Hyperpolarized 3helium magnetic resonance ventilation imaging of the lung in cystic fibrosis: comparison with high resolution CT and spirometry.

  Colm J McMahon, Jonathan D Dodd, Catherine Hill, Neil Woodhouse, Jim M Wild, Stan Fichele, Charles G Gallagher, Stephen J Skehan, Edwin J R van Beek, James B Masterson
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  ABSTRACT: The purpose of this study was to compare hyperpolarized 3helium magnetic resonance imaging (3He MRI) of the lungs in adults with cystic fibrosis (CF) with high-resolution computed tomography (HRCT) and spirometry. Eight patients with stable CF prospectively underwent 3He MRI, HRCT, and spirometry within 1 week. Three-dimensional (3D) gradient-echo sequence was used during an 18-s breath-hold following inhalation of hyperpolarized 3He. Each lung was divided into six zones; 3He MRI was scored as percentage ventilation per lung zone. HRCT was scored using a modified Bhalla scoring system. Univariate (Spearman rank) and multivariate correlations were performed between 3He MRI, HRCT, and spirometry. Results are expressed as mean+/-SD (range). Spirometry is expressed as percent predicted. There were four men and four women, mean age = 31.9+/-9 (20-46). Mean forced expiratory volume in 1 s (FEV)1 = 52%+/-29 (27-93). Mean 3He MRI score = 74%+/-25 (55-100). Mean HRCT score = 48.8+/-24 (13.5-83). The correlation between 3He MRI and HRCT was strong (R = +/-0.89, p < 0.001). Bronchiectasis was the only independent predictor of 3He MRI; 3He MRI correlated better with FEV1 and forced vital capacity (FVC) (R = 0.86 and 0.93, p < 0.01, respectively) than HRCT (R = +/-0.72 and +/-0.81, p < 0.05, respectively). This study showed that 3He MRI correlates strongly with structural HRCT abnormalities and is a stronger correlate of spirometry than HRCT in CF.
  European Radiology 11/2006; 16(11):2483-90. · 3.22 Impact Factor
• Article: The relative roles of magnetic resonance cholangiopancreatography (MRCP) and endoscopic ultrasound in diagnosis of common bile duct calculi: a critically appraised topic.

  Colm J McMahon
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  ABSTRACT: The relative roles of magnetic resonance cholangiopancreatography (MRCP) and endoscopic ultrasound (EUS) in the investigation of common bile duct (CD) calculi were evaluated using "evidence-based practice" (EBP) methods. A focused clinical question was constructed. A structured search of primary and secondary evidence was performed. Retrieved studies were appraised for validity, strength and level of evidence (Oxford/CEBM scale: 1-5). Retrieved literature was divided into group A; MRCP slice thickness >or=5 mm, group B; MRCP slice thickness = 3 mm or 3D-MRCP sequences. Six studies were eligible for inclusion (3 = level 1b, 3 = level 3b). Group A: sensitivity and specificity of MRCP and EUS were (40%, 96%) and (80%, 95%), respectively. Group B: sensitivity and specificity of MRCP and EUS were (87%, 95%) and (90%, 99%), respectively. MRCP should be the first-line investigation for CD calculi and EUS should be performed when MRCP is negative in patients with moderate or high pre-test probability.
  Abdominal Imaging 33(1):6-9. · 1.73 Impact Factor
• Article: The relative roles of magnetic resonance cholangiopancreatography (MRCP) and endoscopic ultrasound in diagnosis of malignant common bile duct strictures: a critically appraised topic.

  Colm J McMahon
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  ABSTRACT: The relative roles of magnetic resonance cholangiopancreatography (MRCP) and endoscopic ultrasound (EUS) in the investigation of malignant common bile duct (CD) strictures were evaluated using "evidence-based practice" (EBP) methodology. A focused clinical question was constructed. A structured search of primary and secondary evidence was performed. Retrieved studies were appraised for validity, strength and level of evidence (Oxford/CEBM scale: 1-5). Three studies were eligible for inclusion; there were 2 level 3b and 1 level 4 papers. One paper included a patient group appropriate to the question and contained sufficient data to allow analysis. Sensitivity and specificity of MRCP and EUS were (90%, 65%) and (80%, 80%), respectively. In the diagnosis of malignant CD strictures, EUS is more specific than MRCP and may allow cytology to be obtained via a trans-duodenal approach. A multi modality imaging approach is recommended.
  Abdominal Imaging 33(1):10-3. · 1.73 Impact Factor